Packaged microelectronic assemblies, such as memory chips and microprocessor chips, typically include a microelectronic die mounted to a substrate (e.g., an interposer board) and encased in a plastic protective covering. The die includes functional features, such as memory cells, processor circuits, and interconnecting circuitry. The die also typically includes die bond pads that are electrically coupled to the functional features. The bond pads are coupled to corresponding first bond pads on the substrate (e.g., with wirebonds), and this connection is protected with the plastic protective covering. The first substrate bond pads can be coupled to second substrate bond pads on an opposite surface of the substrate via pathways that are internal to the substrate. The second bond pads can in turn be connected to external devices, for example, using solder balls. Accordingly, the substrate can have one or more layers of conductive material (e.g., copper) that is etched or otherwise configured to form the first substrate bond pads and the second substrate bond pads.
In a typical operation, the substrate bond pads are built up in an electrolytic plating operation using a bus formed from the conductive layers to transmit electrical current to the bond pads. One drawback with the bus is that it can act as an antenna and can accordingly create extraneous signals, which may interfere with the operation of the microelectronic die. Accordingly, several techniques have been developed for forming bond pads on a substrate without requiring that a bus remain in the substrate. While these techniques have met with at least some success, they have also been subject to several drawbacks. These drawbacks can include undercutting the conductive material at the bond pads and/or difficulty in obtaining very fine pitch spacing between adjacent bond pads. As the size of microelectronic dies continues to decrease, and performance demands on the microelectronic dies continues to increase, these drawbacks can in some cases place undesirable design and/or performance limitations on the microelectronic dies.